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1 – 10 of 560
Article
Publication date: 1 June 1994

Stefka N. Dimova and Daniela P. Vasileva

The problem of finding the possible classes of solution of differentnonlinear equations seems to be of a great importance for many applications.In the context of the…

Abstract

The problem of finding the possible classes of solution of different nonlinear equations seems to be of a great importance for many applications. In the context of the theory of self‐organization it is interpreted as finding all possible structures which arise and preserve themselves in the corresponding unbounded nonlinear medium. First, results on the numerical realization of a class of blow‐up invariant solutions of a nonlinear heat‐transfer equation with a source are presented in this article. The solutions considered describe a spiral propagation of the inhomogeneities in the nonlinear heat‐transfer medium. We have found initial perturbations which are good approximations to the corresponding eigen functions of combustion of the nonlinear medium. The local maxima of these initial distributions evolve consistent with the self‐similar law up to times very close to the blow‐up time.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 4 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 22 August 2022

S.P. Venkatesan, K. Ramachandran, A. John Presin Kumar and Balamurugan G.M.

Aluminum alloy AA5083 is applicable in ship building, military, railway and industry because of its excellent properties like resistance to chemical and sea water attack…

Abstract

Purpose

Aluminum alloy AA5083 is applicable in ship building, military, railway and industry because of its excellent properties like resistance to chemical and sea water attack. However, its performance is affected by weak wear resistance. Hence, this should be solved to improve the performance of AA5083 alloy in the aforementioned fields. The purpose of this research is to enhance the wear properties of AA5083 alloy.

Design/methodology/approach

In this research, AA5083 alloy was reinforced with industrial wastes such as red mud and granite particles using stir casting method. Totally, four types of composites were fabricated, namely, AA5083/3 Wt.% red mud (C1), AA5083/3 Wt.% granite (C2), AA5083/1 Wt.% red mud-2Wt.% granite (C3) and AA5083/2 Wt.% red mud-1Wt.% granite (C4). Wear properties such as mass loss and coefficient of friction (COF) were analyzed for different wear parameters. Further, the mechanical properties like hardness and tensile strength were investigated.

Findings

Results showed that the inclusion of reinforcement particles improved the wear and mechanical properties of AA5083 alloy (C0). The C2 sample displayed the maximum hardness of 87 HV and tensile strength of 317 MPa owing to the inclusion of 3 Wt.% granite particles. Furthermore, the wear study results showed that the C2 sample displayed the minimum mass loss and COF. It was concluded from this research that C2 sample could be a good candidate to be applicable in marine, military, railway and industrial applications with improved performance.

Originality/value

This work is original as the industrial waste is used as reinforcements in the performance improvement of AA5083 aluminum alloy.

Details

Industrial Lubrication and Tribology, vol. 74 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 February 1996

Mervette El‐Batouti

Measures the rates of the copper (II)/steel cementation reaction in organic‐water mixture solvent at 25°C using an atomic absorption spectrophotometer. The relation…

Abstract

Measures the rates of the copper (II)/steel cementation reaction in organic‐water mixture solvent at 25°C using an atomic absorption spectrophotometer. The relation between In C0/C and t in the absence of non‐aqueous solvent and at very diluted CuSO4 solution is given by In C0/C= k.A.t/V, while in the organic‐water mixture the data fit the equation of In C0lC= b+kAt/V. Finds that the rate constant of the cementation reaction increases with increasing the dielectric constant of the mixture. The rate of cementation increased in the order: water > methanol > ethanol > n‐propanol > 2‐propanol.

Details

Anti-Corrosion Methods and Materials, vol. 43 no. 2
Type: Research Article
ISSN: 0003-5599

Article
Publication date: 1 February 1997

Anna Kochan

Describes how Vauxhall Motors has developed new CO2 welding applications for robots at its Ellesmere Port plant on Merseyside, UK. Outlines how, after successfully…

174

Abstract

Describes how Vauxhall Motors has developed new CO2 welding applications for robots at its Ellesmere Port plant on Merseyside, UK. Outlines how, after successfully robotizing the hood welding process, Vauxhall introduced robots for CO2 welding which was difficult for operators to carry out. Explains the process and how robots were successfully developed to fulfil Vauxhall’s requirements.

Details

Industrial Robot: An International Journal, vol. 24 no. 1
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 11 April 2021

Yifan Xu, Xiang Gu, Qinghua Meng, Bin Wang and Jun Fan

This paper aims to show a series of hydrogels with adjustable mechanical properties, which can be cured quickly with visible light. The hydrogel is prepared conveniently…

Abstract

Purpose

This paper aims to show a series of hydrogels with adjustable mechanical properties, which can be cured quickly with visible light. The hydrogel is prepared conveniently with hydroxyethyl acrylate, cross-linker, gelatin and photoinitiator, and can be printed into certain 3D patterns with the direct ink write (DIW) 3D printer designed and developed by the research group.

Design/methodology/approach

In this paper, the authors designed a composite sensitization initiation system that is suitable for hydrogels. The concentration of photoinitiator, gelatin and cross-linker was studied to optimize the curing efficiency and adjust the mechanical properties. A DIW 3D printer was designed for the printing of hydrogel. Pre-gel solution was loaded into printer for printing into established models. The models were made and sliced with software.

Findings

The hydrogels can be cured efficiently with 405-nm visible light. While adding various content of gelatin and cross-linker, the mechanical properties of hydrogels show from soft and fragile (elastic modulus of 121.18 kPa and work of tension of 218.11 kJ·m−3) to rigid and tough (elastic modulus of 505.15 kPa and work of tension of 969.00 kJ·m−3). The hydrogels have high capacity of water absorption. With the DIW 3D printer, pre-gel hydrogel solution can be printed into objects with certain dimension.

Originality/value

In this work, a composite sensitization initiation system was designed, and fast curing hydrogels with adjustable mechanical properties had been prepared conveniently, which has high equilibrium water content and 3D printability with the DIW 3D printer.

Details

Rapid Prototyping Journal, vol. 27 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 31 May 2021

Shiang-Wuu Perng, Horng Wen Wu and Jun-Kuan Wu

The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across.

Abstract

Purpose

The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across.

Design/methodology/approach

The novel design of this study is performed through making the slits in the slab (C1–C3: with slits; C4–C6: without slits) and changing the vertical location of this slab (1/4, 1/2 and 3/4 channel height). The thermal fluid characteristics of all cases are analyzed for various Reynolds numbers (500, 1,000, 1,500 and 2,000) by the SIMPLE-C algorithm.

Findings

The results display that the ribbed slab effectively improves the heat transfer. The slits can modify the flow field in the vortexes around the inclined ribs and remove more heat from this zone to promote the heat transfer. As compared with C0 (without a slab), C2 (the slab with slits and inclined ribs protruding across located vertically on the 3/4 channel height) raises the averaged Nusselt number up to 27.7% at Re = 2,000. As compared with C4 (without slits), C1 (with slits) gains the maximum increase in the averaged Nusselt number by 5.07% at Re = 1,000.

Research limitations/implications

The constant thermo-physical properties of incompressible fluid and the steady flow are considered in this study.

Practical implications

The numerical results will profit the design of heated passageway using a slab with slits and inclined ribs protruding across to acquire better heat transfer promotion.

Originality/value

This slab with slits and inclined ribs protruding across can be applied to the heat transfer promotion and thus be viewed as a useful cooling mechanism in the thermal engineering.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 32 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 June 1993

B.S. MANJUNATHA and T. KANT

This paper attempts to evaluate the transverse stresses that are generated within the interface between two layers of laminated composite and sandwich laminates by using C

Abstract

This paper attempts to evaluate the transverse stresses that are generated within the interface between two layers of laminated composite and sandwich laminates by using Cℴ finite element formulation of higher‐order theories. These theories do not require the use of a fictitious shear correction coefficient which is usually associated with the first‐order Reissner‐Mindlin theory. The in‐plane stresses are evaluated by using constitutive relations. The transverse stresses are evaluated through the use of equilibrium equations. The integration of the equilibrium equations is attempted through forward and central direct finite difference techniques and a new approach, named as, an exact surface fitting method. Sixteen and nine‐noded quadrilateral Lagrangian elements are used. The numerical results obtained by the present approaches in general and the exact surface fitting method in particular, show excellent agreement with available elasticity solutions. New results for symmetric sandwich laminates are also presented for future comparisons.

Details

Engineering Computations, vol. 10 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 1951

V.M. Falkner

Calculations have been carried out on two elliptic wings, with ratios of major to minor axis 2·5 and 5 to 1 respectively, in order to demonstrate the use of vortex…

Abstract

Calculations have been carried out on two elliptic wings, with ratios of major to minor axis 2·5 and 5 to 1 respectively, in order to demonstrate the use of vortex lattice theory in calculating lr and nr by lifting plane theory for wings of arbitrary plan form. Special tables of downwash, required in order to allow for the curvature of the wake, are included, and the origin of the formulae by which these are derived in a form applicable to linear theory is fully described. For the first wing, the calculated results for lr and nr and for local aerodynamic centre, load coefficients, and local lift coefficients are given for the Glauert‐Wieselsberger lifting line solution as well as for lifting plane solutions with three, six and nine control points respectively. The main work on the second wing is concerned with a six‐point lifting plane solution. The results show that there is not a serious difference between lifting line and lifting plane theory, excepting that the former does not give reliable values for the local a.c. For straight wings the six‐point lifting plane solution gives excellent accuracy. The method is applicable to wings of arbitrary plan, but the field of sweptback wings is unexplored and it should not be assumed without check that the relation of accuracy to number of control points is always the same. A further investigation is also required on the formula for nr when sweepback is present. The calculated value of lr for the 5 to 1 elliptic wing is in close agreement with the measured value for this wing obtained by Wieselsberger on a whirling arm. The report is concerned mainly with the calculation of spanwise load grading and local aerodynamic centre, and extension to detailed pressure distribution may require the use of more variables.

Details

Aircraft Engineering and Aerospace Technology, vol. 23 no. 2
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 25 January 2013

Patrick Corsi

Despite an increasingly explicit professional nature, the futures studies field has suffered an increasing constraining to a collection of specific techniques. The purpose

Abstract

Purpose

Despite an increasingly explicit professional nature, the futures studies field has suffered an increasing constraining to a collection of specific techniques. The purpose of this paper is to harness the foundational shortcomings of current futures studies methods, namely the lack of a well‐defined underpinning theory and of rigorous, rational, systematic, repeatable, traceable, documentable, and transferable method. It proposes a rigorous theory for futures studies whereby futures can be logically designed.

Design/methodology/approach

This paper envisages the futures design activity as an extension and a generalization of decision theories and problem solving. The process is made comprehensible and interpretable thanks to a co‐generation referencing between two spaces named Concepts and Knowledge. It works by undertaking a formal mathematical approach on undecidable root concepts, bearing no logical status, by logically expanding them until a validable proposition in the knowledge space is reached. The paper is based on the concept‐knowledge theory (C‐K theory) from Ecole des Mines ParisTech, explains why it is needed, illustrates it and uses it on two illustrative futures studies examples.

Findings

The proposed research opens a new method for designing futures based on the C‐K theory that has the intrinsic capacity of constructing radical innovations for futures scenarios. While setting clear departure from, for example, brainstorming techniques or Delphi‐based methods, it offers a systematic method for designing futures that rests upon solid theoretical foundation that explains the nonsense or contradictions in producing futures.

Research limitations/implications

While the C‐K theory is fully supported by a scientific basis founded on mathematics and is in widening use in domain‐specific industrial sectors at large, it is still being expanded both theoretically and epistemologically. The theory is not aimed at choosing or formulating suitable or appropriate root concepts, this being the role of domain professionals. Its implementation, however coherent, is only as extensive and covering the problematic at hand as the implementers are congruous to the application domain.

Practical implications

The proposed research can help futurists to develop new breakthrough plans, solutions and alternatives with essential and novel benefits: to help control the rationale of a futures scenario development, to control the degree of innovation (e.g. change, reform, progress, create …) to reach, and to bring to decision makers and policy‐makers the traced explanation of different design paths.

Social implications

The benefits of the C‐K approach are detailed and elements founding further theoretical research are provided, including possible developments of C‐K theory specifically helpful for futurists. The research offers a collective design method for revisiting futures sciences by defining, understanding and developing creative futures alternatives that can collectively mobilize stakeholders. Workshops with stakeholders remain necessary, with experienced coaches catalyzing its field implementation.

Originality/value

The paper pushes the edge of the discussion on philosophical, ontological and epistemological grounds and supplies a theoretical underpinning for futures studies at large. The research is inherited from the creative power of modern mathematics as developed and proven by the C‐K theory, a powerful approach for discussing design phenomena. The author argues that it constitutes a suitable and useful asset for futures scientists insofar as to imagine, understand, develop, manipulate, and assess creative futures alternatives. The paper introduces and discusses the notion of futuron, which can be seen as a “logical quantum particle of future”.

Details

On the Horizon, vol. 21 no. 1
Type: Research Article
ISSN: 1074-8121

Keywords

Book part
Publication date: 19 December 2012

Shahram Amini, Michael S. Delgado, Daniel J. Henderson and Christopher F. Parmeter

Hausman (1978) represented a tectonic shift in inference related to the specification of econometric models. The seminal insight that one could compare two models which…

Abstract

Hausman (1978) represented a tectonic shift in inference related to the specification of econometric models. The seminal insight that one could compare two models which were both consistent under the null spawned a test which was both simple and powerful. The so-called ‘Hausman test’ has been applied and extended theoretically in a variety of econometric domains. This paper discusses the basic Hausman test and its development within econometric panel data settings since its publication. We focus on the construction of the Hausman test in a variety of panel data settings, and in particular, the recent adaptation of the Hausman test to semiparametric and nonparametric panel data models. We present simulation experiments which show the value of the Hausman test in a nonparametric setting, focusing primarily on the consequences of parametric model misspecification for the Hausman test procedure. A formal application of the Hausman test is also given focusing on testing between fixed and random effects within a panel data model of gasoline demand.

Details

Essays in Honor of Jerry Hausman
Type: Book
ISBN: 978-1-78190-308-7

Keywords

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